The present invention relates to an injection device with a slide which can be displaced in relation to a housing from a retracted position to an injection position, where the slide comprises a portion-situated within the housing and a portion situated outside the housing, both portions being interconnected through a groove in the housing, where the portion situated outside the housing has a syringe holder for securing of a hypodermic syringe, and where the slide is pretensioned toward the injection position by a spring situated in the housing.
NO 86184 discloses an apparatus for operation of a hypodermic syringe. A syringe holder is displaceable along a guide extending along one side of a box-shaped housing which may be opened by removal of a cover extending in the entire longitudinal direction of the housing. At the guide side of the housing, there is within the latter arranged a tension spring which is tensioned by displacement of the syringe holder to the retracted position of the holder. In the retracted position, the syringe holder is retained by a beak which is fastened rotatably to the housing and which can be released from the holder by means of a guide rod extending in the housing opposite the guide side.
U.S. Pat. No. 3,605,742 discloses an injection device with a box-shaped housing in which an internal syringe holder may be displaced in its longitudinal direction. A hypodermic syringe can be inserted in a recess in the syringe holder, a longitudinal wicket in one side of the housing having to be opened beforehand such that the syringe can pass-through an opening in the wall of the housing. The syringe holder can then be displaced to its retracted position by operation of a handle projecting through the side of the housing. By this displacement, two tension springs fastened at the bottom of the housing and at the upper end of the syringe holder, respectively, and extending each in separate longitudinal recesses in the syringe holder, are tensioned.
U.S. Pat. No. 4,333,459 discloses an injection device with a pistol-shaped housing, along the elongated top side of which a syringe holder can be displaced. The syringe holder has an H-shaped cross section where the bottom legs of the H are constituted by sheets each with its longitudinal groove guided over two guide bolts, the bolts projecting from the sides of the housing. By displacement of the holder to its retracted position, is a tension spring arranged under the holder and between the upright side walls of the housing is tensioned. The syringe holder can be released from the retracted position by operation of a pistol grip.
U.S. Pat. No. 4,026,288 discloses further a pistol-shaped injection device where the syringe holder is guided on a bar-shaped guide. A spring is arranged around the guide for propulsion of the holder in order to inject the needle of the syringe in a skin area. By displacement of the syringe holder, a gearwheel is rotated via a rack on the holder, and a pistol grip blocks in its passive position this gearwheel such that the holder is secured. By operation of the grip, the holder is released.
The object of the present invention is to provide an injection device simple as to construction and with a more stable function than the known devices.
For this purpose, the device according to the invention is characterized in that the housing at the groove is constituted by a tube part, the outer and/or inner surface of which forms a guide for the slide, and that the slide has one or more contact faces which are in contact with the guide at least at three areas distributed over more than the half of the circumference of the tube part.
By the fact that the housing itself acts as a tubular guide for the slide, a circumferential face of the guide can be obtained with a larger circumference than if the guide is a separate element within the housing, and thus a more rigid guide is obtained, and by letting at the same time the slide glide on the guide at at least three areas distributed over more than the half of the circumference of the tube part, the slide is retained on the guide in an exact and stable guidance. The rigid guide and the exact guidance result together in an extremely reliable performance. A tubular housing is moreover very simple to produce.
In an advantageous embodiment, the slide portion situated outside the housing encircles the tube part along the entire circumference of the tube part. Thus, an even more stable guidance is obtained as the slide can have contact points in touch with the guide around the complete circumference of the guide, either a continuous face or discrete faces, and as the slide in itself can be more rigid because of the tubular form. Furthermore, the slide arranged around the housing forms a stable and an easy accessible finger grip for operation of the slide by retraction of this for tensioning of the spring.
The outside diameter of the tube part can advantageously be at least 8 mm, and preferably at least 12 mm, a more secure grip around both the housing of the injection device and the slide being thus obtained. Furthermore, as a consequence of additional thickness of material, the total weight of the device can preferably be at least 40 g, and further preferably at least 60 g, the total inertia of the device thus assuring a more steady handling of the device at the operation, and thus a more exact and stable injection.
In an embodiment, an elongated release mechanism extends coaxially with the tube part in the housing and carries a pawl which is spring-loaded to engage with and retain the slide in the retracted position of the slide, the release mechanism can at a first end of the housing cooperate with a release button such that when actuating the release button, the pawl can be disengaged from the slide, and the pre-tensioning spring of the slide is arranged around the release mechanism. In this way, a substantially rotationally symmetrical structure of the device is made possible, which simplifies both the production of the required components and their mounting. It is further possible to use one single spring which is strong enough for the pretensioning of the slide, as the spring can have an outside diameter which is merely a little smaller than the inside diameter of the housing. It is also an advantage that the release button can be placed at one end of the housing as this provides an easy operation, e.g. the button can be designed for axial displacement in the housing at the release.
In an embodiment simple as to production, the release mechanism comprises a release tube with a rod which can be displaced axially in the tube, and the pawl is pivotally journalled in a recess in the rod and has an end which can project through a slit in the release tube, and which at displacement of the rod can be swung into the tube. Thus, also the mounting is facilitated as the release mechanism can be assembled separately and then guided into the housing from the end of the housing.
The portion of the slide situated within the housing can encircle the release mechanism which facilitates the mounting further as the release mechanism can be guided into the housing and through the slide with the slit for the pawl facing an arbitrary direction since the pawl can thus enter into engagement with the slide in any angle position of the release tube in relation to the slide. The portion of the slide situated within the housing can further preferably close the cavity between the release mechanism and the internal surface of the tube part. Thus, at the end of the movement of the slide at injection, an overpressure of air can be created under the slide, whereby a soft braking of the movement of the slide is obtained.
In another embodiment, the release mechanism is provided with a locking mechanism which is spring loaded for locking the pawl in the engagement position of the pawl with the slide and which can release the pawl for releasing by operation of a lock button. This assures the slide not being released unintentionally before the injection device is placed above the skin area where the injection is to be made. The locking mechanism being spring loaded for locking the pawl, the locking is effected automatically by return of the slide without any further operation of the locking mechanism. Before the injection can be made, the lock button has thus to be actuated and it further has to be pressed against the spring load during the release itself of the slide. It is thus prevented that the actuation of the lock is forgotten or that the lock is brought out of function by mistake.
In a particularly easy-to-operate and simple embodiment, the rod, of the release mechanism has a circumferential groove with which a lever can engage when the rod is in its inactivated position where the pawl can engage with the.slide, and the lock button is designed as a lock ring which when turned coaxially about the rod can lift the lever out of engagement with the groove. By designing the lock button as a lock ring, the button can first be turned by means of two fingers and then retained by these two fingers and at the same time the fingers retain the housing itself, the fingers being able to seize both the ring and the housing. The lock ring can preferably be situated at the release button as both the lock ring and the release button in this way can be operated by the fingers of the same hand. The other hand is thus free possibly to control the other end of the device at the skin area where the injection is to be made.
The syringe holder can be detachably fastened on the slide whereby different holders fitting different types of injection syringes can be used. The holder can preferably be designed to be fastened by insertion in a key slot where it is retained by a resilient bow in engagement with the slide so that it can be detached form the slide by pressing back the bow.
In a particularly practical embodiment, the housing has at its other end a lamp which can be lit by actuation of an axially projecting push button. When placing the injection device at a skin area, the push button can thus be activated automatically, as the end of the device with the projecting button is pressed against the skin area whereby the skin area can be illuminated by the lamp for inspection of the area, e.g. a vein can be made visible. Furthermore, the lamp can transilluminate a hypodermic syringe mounted on the holder when the latter is in the injection position. It can thus be detected if any blood can be drawn back in the syringe which indicates that a vein has been hit.
The housing can moreover at its other end have a bow which can be pressed against and extend a skin surface where an injection is to be made. The bow can preferably be made of light transmitting material, such as limpid plastic, and can be adapted such that it can be illuminated by the lamp. The bow can thus guide the light toward the skin area to be inspected.